Coding Decoding

Coding Decoding

Coding-Decoding topic is a very important topic from exam point of view. Questions from this topic is asked in most of the exams.
In Coding Decoding, a set of letters or numbers are given in code which have to be deciphered or decoded.
 

Before moving to questions you should memorise the Position Number of letters in the alphabet.

 
A 1 N 14
B 2 O 15
C 3 P 16
D 4 Q 17
E 5 R 18
F 6 S 19
G 7 T 20
H 8 U 21
I 9 V 22
J 10 W 23
K 11 X 24
L 12 Y 25
M 13 Z 26
 
 
Note: You donot need to memorise the Reverse Number of letters in Alphabet. You can find the Reverse Postition by using the below formula.
 

Reverse Position Number of Alphabet = (26 - Postition Number of Alphabet +1)

eg. 
Reverse Position Number of C = 26 -3 + 1 = 24
Reverse Position Number of P = 26 -16 + 1 = 11
 

The Word EJOTY is very helpful in finding the position of the alphabet as:

 
E J O T Y
5 10 15 20 25
 

The below pattern is very helpful in remembering the Opposite letter of each letter in the alphabet:

 
A B C D E F G H I J K L M
Z Y X W V U T S R Q P O N
 

Coding-Decoding questions asked in exams are bascially of 3 types:

1. Letter to Letter

In this type, certain letters of alphabet stand for certain other letters of alphabet.
 
eg. CROWN --> DSPXO
In this each alphabet is replaced by (Current Position + 1).
C(3) = 3+1 =4 = D
R(18) = 18+1 = 19 = S
O(15) = 15+1 = 16 = P
W(23) = 23+1 = 24 = X
N(14) = 14+1 = 15 = O
 
Example: If MADRAS is coded as NBESBT. How is BOMBAY coded in that code?
(a) CPNCPX
(b) CPNCBZ
(c) CPOCBZ
(d) CQOCBZ
(e) None of these
 
Ans: CPNCBZ
 
Explanation: 
Now you can see that in the above example each letter in the word MADRAS is moved one step forward to obtain the corresponding letter of the code. M is coded as N, A is coded as B and so on.
 
M A D R A S
N B E S B T
 
So code for
B O M B A Y is
C P N C B Z
Likewise code may be moved one step backward also.
 

2. Letter to Number

In this type, letters are changed by the numbers. 
 
eg.
BAD = 214 (Here each letter is changed by its Position in Alphabet)
ZOO = 11212 (Here each letter is changed by its Reverse Position in Alphabet i.e. Z by 1, O by 12
 
Example:
If ZODES is coded as 46321, how will you code the word DOSE?
a) 1234        
b) 4321        
c) 3621        
d) 3612
 
Solution: 
Here, you will observe that all the letters of DOES are included in the letters of ZODES, 
for which you have the code D = 3, O = 6, E = 2, S = 1. Therefore DOES = 3612. So, the answer is (d).

3. Number to Word

In this type each number represents a word.
 
Example:
In a certain code ‘415’ means ‘milk is hot’; ‘18’ means ‘hot soup’; and ‘895’ means ‘soup is tasty’. What number will indicate the word ‘tasty’?
a) 9    b) 8    c) 5    d) 4
Solution:
The code for ‘hot’ is 1. So, the code of ‘soup’ is 8. Now the code of ‘is’ is 5. Hence we can say that the code of ‘tasty’ is 9. So, the answer is (a)
 
 

How to easily  memorise the Position Number of letters in the alphabet:

Every day write some 5-10 random words and assign the positon number to each alphabet. Follow this for 4-5 days you will find that you have memorised all the Position Number of letters in the alphabet.